NexusMPC5566 Microcontroller Reference Manual, Rev. 2Freescale Semiconductor 25-9125.17.6.1 Watchpoint MessagingEnabling watchpoint messaging is accomplished by setting the watchpoint messaging enable bit,DC1[WEN]. Using the BWC1 and BWC2 registers, two independently controlled internal watchpointscan be initialized. When a DMA access address matches on BWA1 or BWA2, a watchpoint message istransmitted.The Nexus module provides watchpoint messaging using the TCODE. When either of the two possiblewatchpoint sources asserts, a message is sent to the queue to be messaged out. This message indicates thewatchpoint number.Figure 25-69. Watchpoint Message Format25.17.6.2 Watchpoint Error MessageAn error message occurs when a new message cannot be queued due to the message queue being full. TheFIFO discards messages until it has completely emptied the queue. After it is emptied, an error message isqueued. The error encoding indicates which types of messages attempted to be queued while the FIFO wasbeing emptied.If only a watchpoint message attempts to enter the queue while it is being emptied, the error messageincorporates the watchpoint only error encoding (00110). If a data trace message also attempts to enter thequeue while it is being emptied, the error message incorporates error encoding (01000).Error information is messaged out in the following format (refer to Figure 25-70).Figure 25-70. Error Message FormatTable 25-61. Watchpoint Source DescriptionWatchpoint Source (4 bits) Watchpoint DescriptionXXX1 ReservedXX1X ReservedX1XX Internal Watchpoint #1 (BWA1 match)1XXX Internal Watchpoint #2 (BWA2 match)WPHIT (XXXX)MSB LSB12SRC TCODE (001111)36 bits4 bits4 bitsFixed length = 14 bitsECODE (00110 / 01000)MSB LSB12SRC TCODE (001000)36 bits4 bits5 bitsFixed length = 15 bits
